The occupant of a vehicle equipped with pyrotechnically deployed restraints must be reliably classified in order to determine whether (and how forcefully) the restraints should be deployed when a crash occurs. For example, it is generally desired to enable deployment for a normally seated adult occupant, and to disable deployment in the case of an infant or child car seat that is placed on the vehicle seat and cinched down with a seat belt. In systems where the occupant is classified based on a measure of the force applied to the seat, it can be difficult to reliably distinguish between a normally seated adult and a tightly cinched car seat, as both apply similar seat force.
One way of distinguishing between a normally seated adult and a cinched car seat is to analyze the dynamic characteristics of the seat force and other correlative dynamic parameters such as z-axis vehicle acceleration. See, for example, the U.S. Pat. No. 6,246,936 to Murphy et al. and the U.S. Pat. No. 6,542,802 to Gray et al., both of which are assigned to the assignee of the present invention. However, it can be difficult to identify a single characteristic or set of characteristics for reliably distinguishing between a normally seated adult and a cinched car seat under the various operating conditions a vehicle might encounter. In practice, there are typically several possible dynamic characteristics that are correlative of a given occupant classification, and the degree of correlation for any given characteristic will often vary depending on occupant and vehicle-related conditions. Accordingly, what is needed is an easily implemented way of distinguishing between a normally seated adult and a cinched car seat of similar apparent weight based a number of correlative dynamic characteristics for the two classifications.